1. Field
The present invention relates to the thermal management of a battery charging system. Controlling the heat flow from the circuit that converts analog power to a digital charging pulse to the battery under charge is necessary to ensure a fast and complete charge without any degradation of that battery. Lithium ion batteries are particularly susceptible to the influences of temperature while under charge and are typically required to have their charging suspended when the battery temperature reaches 45° Celsius.
2. Description of Related Art
There have been previous attempts to control the heat transferred from the charging circuit to the batteries under charge. Some designs have ignored the problem of the heat from charging circuit components reaching the battery(s) under charge and have modified their battery charging parameters to keep the battery temperatures within the recommended limits. In the past this was done by adjusting the voltage and charging cycles when the temperature measurement means of the battery under charge had reached certain predetermined limits. This, however, increased the time required to charge the battery, added cost, complexity and another potential failure point of the charging unit. Other approaches included adding cooling fins to the unit to transfer the heat generated by the charging circuit. However this adds weight and size to the battery charger. The amount of heat carried away is largely dependent on the ambient temperature and the amount of air flow circulating around the fin. Still another method has included increasing the physical distance of the battery under charge from the charging circuit board as seen in U.S. Pat. No. 6,710,577 issued to King Mo Shum for Battery Charger and patent application Ser. No. 11/649,057 by David Nierescher for Thermal Management of Battery Charging Systems. Both of these methods increase the size of the footprint required by the charger.